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a walk in the park: part II

Gracing the downtown Los Angeles skyline at 111 South Grand Avenue is the Walt Disney Concert Hall, whose structure bears the unmistakable imprint of its designer, Frank Gehry. As we saw in the Part I post on Gehry's design for Chicago's Pritzer Pavilion, he's quite fond of using stainless steel curved surfaces, and the Disney Hall is no exception. But his choice to polish those surfaces to a mirror-like shine for the Los Angeles performance venue had an unexpected consequence when it finally opened in 2003: downtown LA is far more residential these days, and people living in nearby condo and apartment buildings were plagued by chronic, blinding glare as the perennial sunshine was reflected off those shiny surfaces. The effect was similar to that of a parabolic mirror, concentrating the reflected light so effectively that certain "hot spots" were created on nearby sidewalks, reaching temperatures as high as 140 degrees F. Residents experienced their own "hot spots," in the form of rooms directly exposed to the reflections, which in turn caused A/C costs to skyrocket for the affected units. It proved to be a fairly easy fix: after identifying the offending surfaces using computer analysis, they simply sanded them down to reduce the glare to reasonable levels. Ad the Disney Hall has co-habitated peacefully with downtown's residents ever since.

I mostly bring it up because another distinguishing feature of Chicago's Millennium Park is the modern art sculpture officially titled "Cloud Gate," although locals quickly dubbed it "the Bean" because of its kidney-bean shape. It rises three stories and weighs 110 tons, and is the creation of the artist Anish Kapoor (who initially resisted the moniker of "the Bean" for his masterpiece, but has since come to embrace it). The Bean is another highly polished, reflective steel structure, intended to resemble a drop of mercury hovering just at the point of landing, but in this case, the structure was sanded to a smooth polish to enhance the reflections by getting rid of the visible seams between the 168 steel plates that make up the sculpture. The result is strikingly warped reflections of people, the city buildings, even the sky, captured within the curved, mirror-like surface.

The Bean has proved tremendously popular with both locals and tourists, perhaps because we all love shiny things, or perhaps because deep down, we all have an element of Narcissus in us. Witness the enduring popularity of fun house mirrors, and our fascination with the way they reflect skewed images of our selves. That's why most science museums have some kind of exhibit element that incorporates the basic optics behind mirrors. And it's probably a big reason why the Bean is so immensely popular.

You sometimes get ghostly partial reflections in glass windows -- an effect that Richard Feynman explained eloquently in his QED lectures as arising from the way photons interact with the glassy matter (the vast majority of photons hitting a pane of glass are either absorbed or pass right through, but a small number are reflected back, producing a partial reflection). Unlike window panes, however, mirrors are "silvered" on one side with tin or mercury, making the reflections that much stronger (because more photons are reflected back).

We all learned the basic maxim of mirrors and light in science class: the angle of incidence is equal to the angle of reflection. And we know from personal experience that a concave mirror will make you seem taller, while a convex mirror makes you seem shorter, because instead of hitting your eyes in a normal perpendicular line, the reflected light hits your eyes slightly above or below that perpendicular line. (There was one particular mirror in my former Brooklyn dojo that we all swore took off 10 pounds: all the older guys wanted to do their forms in front of it.)

Curved glass surfaces are the principle behind lenses, and curved mirrors can be used to concentrate light in, say, telescopes or solar cookers -- or chic condos in downtown Los Angeles. The San Francisco Exploratorium has a very nice online set of activities examining the science behind parabolic and spherical reflections. (The latter ingeniously employs silver Christmas tree balls packed in a box to create an array of spherical reflectors.) It's worth checking out, especially if you're planning on visiting the Bean: the most striking is the parabolic effect of the sculpture is seen in the Bean's underbelly, which Kapoor calls the "omphalos" or navel of the sculpture: there, in addition to being warped, people's reflections are multiplied -- another popular fun house effect.

Reflecting pools are another popular feature of many parks, and Millennium Park boasts one, too: a black granite one, measuring 232 feet in length, part of the interactive public fountain called Crown Fountain, designed by Spanish sculptor Jaume Plensa. It's shallow water, a mere eighth of an inch deep, but it's enough to refresh the crowds scampering around the fountain on a hot summer day. (The water feature is only active from mid-spring through mid-fall, given Chicago's notoriously cold winters.) It looks a bit like one is walking on water, a boon to those with a Messiah complex.

On either side of the reflecting pool are two 50-foot glass block towers, facing each other. Underneath those glass bricks are cutting-edge LED video screens that, when illuminated, showcase videos of the faces of nearly 1000 Chicago residents, in random rotation, all smiling out at the world while a stream of water cascades over their visages. Every so often, the person in the video will open his or her mouth, and carefully placed nozzles will spray water into the center of the pond -- as if the faces were spewing the water directly onto the populace, much like the gargoyles found in older historical fountains. Needless to say, kids love it.

A great deal of science went into making the Crown Fountain the artistic and technological wonder that it is, well worth the $17 million price tag. The hydraulics must have been the easy part: you just pump the water and recirculate it through the fountain, as with any other such structure. Crown Fountain just needs dual pump rooms below each tower, drawing water from a reservoir beneath the reflecting pool. The towers are built around a special stainless steel T-frame, strong enough to bear the load of the 50-foot walls made of glass bricks, and to withstand the Chicago winds. Those glass bricks were custom-made by hand at a factory in Pittsburgh: white glass, not the usual green glass (which is the result of iron impurities). The glass had to be thin enough to avoid image distortion, and only one of the six faces of the block is polished; the rest are textured.

But the most central technology that makes the Crown Fountain possible is the light-emitting diode (LED). We take LED screens for granted these days, forgetting that they really are somewhat wondrous. LEDS are basically solid state devices mounted on a substrate of clear plastic, glass or foil. Typically, there is a transparent anode layer that injects "holes," and a cathode layer that injects electrons when a current is applied across the device. Sandwiched between those two layers are hole- and electron-transporting layers, separated by an emissive layer. It's the emissive layer that (duh) emits light when a voltage is applied. The color of the light depends on the type of semiconducting material is used.

So at heart, LEDS are tiny light bulbs that fit easily into an electrical circuit, except the illumination comes solely from the movement of electrons in the semiconductor material. There is no need for a filament, so they don't burn out, nor do they get especially hot (unless there are large arrays of them housed inside a glass tower, like the Crown Fountain). Less heat means less energy is wasted, leaving more electrical energy devoted to illumination. LEDs used to be quite pricey, but as semiconducting materials costs have lowered, the technology has become more affordable. Crown Fountain uses approximately 70 units per tower of color-changing LED lighting fixtures. The natural advantages and disadvantages of LEDs had to be taken into account when designing Crown Fountain. The advantages are obvious: LEDs are efficient, cost-effective and long-lasting, and Plensa intends his piece to last a century or more.

The disadvantages might be less obvious to someone unfamiliar with the technology. Not only did the structure need to be robust enough to support the weight of the LED arrays, but the displays had to be legible even in daylight (which can be quite bright in Chicago on a clear day), and steps had to be taken to combat heat buildup. The latter was easily address by adding fans to cool the air at the bottom before it works its way through the chimney-like tower, and we've already seen how the T-frame structure was chosen for its load-bearing properties. (Side note: the individual glass blocks are actually removable for cleaning and repair, without disrupting the overall display.) For optimal viewing, Plensa chose low- rather than high-resolution images, which were also less expensive. Black fins were placed in the screens to keep direct sunlight from hitting the LEDs -- anyone who's tried to use their laptop in direct sunlight knows why this is so important.

LED technology is constantly evolving, and a subclass known as organic light-emitting diodes (OLEDs) are now blazing their own path to commercial glory. It's already big business: the market for OLEDs is estimated at around $1.4 billion, expected to increase to $10.9 billion by 2012. You see OLEDs around you all the time: they're used in the small screens in cell phones, PDAs, digital cameras, and portable music players, although they have yet to break into full-sized display or TV applications, despite the best efforts to date of corporate giants like Kodak, Sony, Dupont and Universal Display Corporation.

OLEDs are organic, so they degrade over time and are easily damaged by exposure to water, making them unsuitable for long-life watery applications like, say, the Crown Fountain. But polymer OLEDs bring the advantage of a thin, flexible substrate that can be printed with just standard inkjet printer technology instead of expensive lithographic etching, for example. They're more easily integrated with other electronic components, too, and that flexibility could one day lead to roll-up displays or even displays embedded in clothing. OLEDs also show a great deal of promise as eventual cheap, disposable microarrays of chemical and biologicalsensors which light up in the presence of toxic compounds or gases.

Plensa chose to use LED technology in his Crown Fountain piece because he was familiar and comfortable with the technology -- it had become commonplace enough that he was able to use LED fixtures in several earlier projects. I can't wait to see how modern artists choose to use OLEDs as they become more broadly available commercially -- especially the flexible polymer versions. One can imagine a Crown Fountain that bends with the winds, or displays of fabric embedded with OLED sensors to create constantly changing images on cloth. Science begets technology, and more and more these days, cutting-edge technology is giving rise to fascinating and innovative new forms of art. Who knows what the future will bring?

Physics Cocktails

Heavy G

The perfect pick-me-up when gravity gets you down.
2 oz Tequila
2 oz Triple sec
2 oz Rose's sweetened lime juice
7-Up or Sprite
Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.

Any mad scientist will tell you that flames make drinking more fun. What good is science if no one gets hurt?
1 oz Midori melon liqueur
1-1/2 oz sour mix
1 splash soda water
151 proof rum
Mix melon liqueur, sour mix and soda water with ice in shaker. Shake and strain into martini glass. Top with rum and ignite. Try to take over the world.